Resist composition and method of forming resist pattern

ABSTRACT

A resist composition including a base component (A) which exhibits changed solubility in a developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, the acid-generator component (B) including at least one acid generator (B1) represented by general formula (b1) shown below, at least one acid generator (B2) represented by general formula (b2) shown below, and at least one acid generator (B3) represented by general formula (b3) shown below (wherein IV to R3 each independently represents a cyclic group which may have a substituent, a chain alkyl group, or a chain alkenyl group; Y1 represents a single bond or a divalent linking group containing an oxygen atom; M1+ to M3+ represents a monovalent organic cation; n represents an integer of 1 to 4; m represents an integer of 0 to 4; provided that, when m is 0, the carbon atom adjacent to the sulfur atom within R2 has no fluorine atom bonded thereto).R1—Y1—(CF2)n—SO3−M1+  (b1)R2—(CH2)m—SO3−M2+  (b2)R3—COO−M3+  (b3)

TECHNICAL FIELD

The present invention relates to a resist composition and a method offorming a resist pattern.

Priority is claimed on Korean Patent Application No. 2015-0144911, filedOct. 16, 2015, the content of which is incorporated herein by reference.

DESCRIPTION OF RELATED ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

A resist material in which the exposed portions become soluble in adeveloping solution is called a positive-type, and a resist material inwhich the exposed portions become insoluble in a developing solution iscalled a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength (increasing the energy) of the exposure light source.Conventionally, ultraviolet radiation typified by g-line and i-lineradiation has been used, but nowadays KrF excimer lasers and ArF excimerlasers are starting to be introduced in mass production. Furthermore,research is also being conducted into lithography techniques that use anexposure light source having a wavelength shorter (energy higher) thanthese excimer lasers, such as electron beam, extreme ultravioletradiation (EUV), and X ray.

In recent years, due to prolonging of ArF lithography, demands arebecoming more strict when conducting lithography in terms of reducingroughness and reducing fluctuation of hole size (CD). A method is knownin which an photoacid generator having a free anion with relatively weakacidity is used as an acid diffusion control agent (quencher), so as toimprove dissolution contrast between exposed portions and unexposedportions (Patent Literature 1).

DOCUMENTS OF RELATED ART Patent Literature

-   [Patent Literature 1] Japanese Unexamined Patent Application, First    Publication No. 2009-244352

SUMMARY OF THE INVENTION

However, as the pattern becomes finer, the light diffraction is reachinga limit, the contrast of light is deteriorated. As a result, in the caseof a conventional resist composition, when a pattern is formed with aweak contrast of light, acid is generated more than necessary, therebybecoming a source of roughness.

The present invention takes the above circumstances into consideration,and the present inventors have newly found that, in order to suppressthe above phenomenon, addition of a photoacid generator having a mediumacid strength is effective in functioning for both acid generation andacid diffusion control.

Such effect can be achieved by virtue of including, at the same time, aphotoacid generator having a fluoroalkylsulfonic acid which is anextremely strong acid as an anion, a photoacid generator having asulfonic acid which is a strong acid as an anion, and a photoacidgenerator having a carboxylic acid which is a weak acid as an anion. Anobject of the present invention is to provide a resist compositionexhibiting excellent lithography properties by virtue of including suchphotoacid generators, and a method of forming a resist pattern by usingthe resist composition.

For achieving the above object, the present invention employs thefollowing configuration.

A first aspect of the present invention is a resist compositionincluding a base component (A) which exhibits changed solubility in adeveloping solution under action of acid and an acid-generator component(B) which generates acid upon exposure, the acid-generator component (B)including at least one acid generator (B1) represented by generalformula (b1) shown below, at least one acid generator (B2) representedby general formula (b2) shown below, and at least one acid generator(B3) represented by general formula (b3) shown below.[Chemical Formula 1]R¹—Y¹—(CF₂)_(n)—SO₃ ⁻M₁ ⁺  (b1)R²—(CH₂)_(m)—SO₃ ⁻M₂ ⁺  (b2)R³—COO⁻M₃ ⁺  (b3)

In the formulae, R¹ to R³ each independently represents a cyclic groupwhich may have a substituent, a chain alkyl group, or a chain alkenylgroup; Y¹ represents a single bond or a divalent linking groupcontaining an oxygen atom; M₁ ⁺ to M₃ ⁺ represents a monovalent organiccation; n represents an integer of 1 to 4; m represents an integer of 0to 4; provided that, when m is 0, the carbon atom adjacent to the sulfuratom within R² has no fluorine atom bonded thereto.

A second aspect of the present invention is a method of forming a resistpattern, including: using a resist composition according to the firstaspect to form a resist film on a substrate, exposing the resist film,and developing the resist film to form a resist pattern.

According to the present invention, there are provided a resistcomposition which exhibits excellent lithography properties, and amethod of forming a resist pattern using the resist composition.

DETAILED DESCRIPTION OF THE INVENTION

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified.

The term “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent(R^(α)) with which the hydrogen atom bonded to the carbon atom at theα-position is substituted is an atom other than the hydrogen atom or agroup, and examples thereof include an alkyl group having from 1 to 5carbon atoms, a halogenated alkyl group having from 1 to 5 carbon atoms,and a hydroxyalkyl group. A carbon atom on the α-position of an acrylateester refers to the carbon atom bonded to the carbonyl group, unlessspecified otherwise.

Hereafter, an acrylate ester having the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent issometimes referred to as “α-substituted acrylate ester”. Further,acrylate esters and α-substituted acrylate esters are collectivelyreferred to as “(α-substituted) acrylate ester”.

A “structural unit derived from a hydroxystyrene derivative” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of hydroxystyrene or a hydroxystyrene derivative.

The term “hydroxystyrene derivative” includes compounds in which thehydrogen atom at the α-position of hydroxystyrene has been substitutedwith another substituent such as an alkyl group or a halogenated alkylgroup; and derivatives thereof. Examples of the derivatives thereofinclude hydroxystyrene in which the hydrogen atom of the hydroxy grouphas been substituted with an organic group and may have the hydrogenatom on the α-position substituted with a substituent; andhydroxystyrene which has a substituent other than a hydroxy group bondedto the benzene ring and may have the hydrogen atom on the α-positionsubstituted with a substituent. Here, the α-position (carbon atom on theα-position) refers to the carbon atom having the benzene ring bondedthereto, unless specified otherwise.

As the substituent which substitutes the hydrogen atom on the α-positionof hydroxystyrene, the same substituents as those described above forthe substituent on the α-position of the aforementioned α-substitutedacrylate ester can be mentioned.

A “structural unit derived from vinylbenzoic acid or a vinylbenzoic acidderivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of vinylbenzoic acid or a vinylbenzoic acidderivative.

The term “vinylbenzoic acid derivative” includes compounds in which thehydrogen atom at the α-position of vinylbenzoic acid has beensubstituted with another substituent such as an alkyl group or ahalogenated alkyl group; and derivatives thereof. Examples of thederivatives thereof include benzoic acid in which the hydrogen atom ofthe carboxy group has been substituted with an organic group and mayhave the hydrogen atom on the α-position substituted with a substituent;and benzoic acid which has a substituent other than a hydroxy group anda carboxy group bonded to the benzene ring and may have the hydrogenatom on the α-position substituted with a substituent. Here, theα-position (carbon atom on the α-position) refers to the carbon atomhaving the benzene ring bonded thereto, unless specified otherwise.

A “styrene derivative” refers to a compound in which the hydrogen atomon the α-position of styrene is substituted with a substituent such asan alkyl group, a halogenated alkyl group or the like.

A “structural unit derived from styrene” or “structural unit derivedfrom a styrene derivative” refers to a structural unit that is formed bythe cleavage of the ethylenic double bond of styrene or a styrenederivative.

As the alkyl group as a substituent on the α-position, a linear orbranched alkyl group is preferable, and specific examples include alkylgroups of 1 to 5 carbon atoms, such as a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group as the substituent onthe α-position include groups in which part or all of the hydrogen atomsof the aforementioned “alkyl group as the substituent on the α-position”are substituted with halogen atoms. Examples of the halogen atom includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable.

Specific examples of the hydroxyalkyl group as the substituent on theα-position include groups in which part or all of the hydrogen atoms ofthe aforementioned “alkyl group as the substituent on the α-position”are substituted with a hydroxy group. The number of hydroxy groupswithin the hydroxyalkyl group is preferably 1 to 5, and most preferably1.

The expression “may have a substituent” means that a case where ahydrogen atom (—H) is substituted with a monovalent group, or a casewhere a methylene group (—CH₂—) is substituted with a divalent group.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

<<Resist Composition>>

A first aspect of the present invention is a resist composition whichgenerates acid upon exposure and exhibits changed solubility in adeveloping solution under action of acid, the resist compositionincluding a base component (A) which exhibits changed solubility in analkali developing solution under action of acid and an acid-generatorcomponent (B) which generates acid upon exposure, the acid-generatorcomponent (B) including at least one acid generator represented by theaforementioned general formula (b1), at least one acid generatorrepresented by the aforementioned general formula (b2) shown below, andat least one acid generator represented by the aforementioned generalformula (b3).

In the present embodiment, the resist composition contains a basecomponent (A) (hereafter, referred to as “base component (A)”) whichexhibits changed solubility in a developing solution.

When a resist film is formed using the resist composition and the formedresist film is subjected to a selective exposure, acid is generated atexposed portions, and the generated acid acts on the component (A) tochange the solubility of the component (A) in a developing solution,whereas the solubility of the component (A) in a developing solution isnot changed at unexposed portions, thereby generating difference insolubility in a developing solution between exposed portions andunexposed portions. Therefore, by subjecting the resist film todevelopment, the exposed portions are dissolved and removed to form apositive-tone resist pattern in the case of a positive resist, whereasthe unexposed portions are dissolved and removed to form a negative-toneresist pattern in the case of a negative resist.

In the present specification, a resist composition which forms apositive resist pattern by dissolving and removing the exposed portionsis called a positive resist composition, and a resist composition whichforms a negative resist pattern by dissolving and removing the unexposedportions is called a negative resist composition.

In the present embodiment, the resist composition may be either apositive resist composition or a negative resist composition. Further,the resist composition of the present invention may be used in a dualtone developing process.

Further, in the present embodiment, the resist composition may beapplied to an alkali developing process using an alkali developingsolution in the developing treatment, or a solvent developing processusing a developing solution containing an organic solvent (organicdeveloping solution) in the developing treatment, and preferably asolvent developing process.

The resist composition usable in forming a resist pattern has a functionof generating acid upon exposure The resist composition contains anacid-generator component (B), and the component (A) may be capable ofgenerating acid upon exposure.

In the case where the component (A) generates acid upon exposure, thecomponent (A) is a “base component which generates acid upon exposureand exhibits changed solubility in a developing solution under action ofacid”. In the case where the component (A) is a base component whichgenerates acid upon exposure and exhibits changed solubility in adeveloping solution under action of acid, the component (A1) describedlater is preferably a polymeric compound which generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid. As the polymeric compound, a resin having a structuralunit which generates acid upon exposure can be used. As the structuralunit which generates acid upon exposure, a conventional structural unitcan be used.

<Component (A)>

In the present invention, the term “base component” refers to an organiccompound capable of forming a film, and is preferably an organiccompound having a molecular weight of 500 or more. When the organiccompound has a molecular weight of 500 or more, the film-forming abilityis improved, and a photosensitive resin pattern of nano level can beeasily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. Hereafter, a “resin” refers to a polymer havinga molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

As the component (A′), a resin, a low molecular weight compound, or acombination thereof may be used.

The component (A) is a base component which exhibits increasedsolubility in a developing solution under action of acid.

In the present invention, the component (A) may be a component thatgenerates acid upon exposure.

In the present embodiment, the component (A) preferably contains apolymeric compound (A1) having a structural unit containing an aciddecomposable group which exhibits increased polarity by the action ofacid (hereafter, referred to as “structural unit (a1)”), a structuralunit derived from an acrylate ester containing an —SO₂— containingcyclic group, a lactone-containing cyclic group, a carbonate-containingcyclic group or any other heterocyclic group (hereafter, referred to as“structural unit (a2)”), and a structural unit containing a polargroup-containing aliphatic hydrocarbon group (hereafter, referred to as“structural unit (a3)”).

(Structural Unit (a1))

The structural unit (a1) is a structural unit containing an aciddecomposable group that exhibits increased polarity by the action ofacid.

The term “acid decomposable group” refers to a group in which at least apart of the bond within the structure thereof is cleaved by the actionof an acid.

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, anamino group and a sulfo group (—SO₃H). Among these, a sulfo group or apolar group containing —OH in the structure thereof (hereafter, referredto as “OH-containing polar group”) is preferable, a carboxy group or ahydroxy group is more preferable, and a carboxy group is particularlydesirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) can be given.

Here, the “acid dissociable group” includes:

(i) a group in which the bond between the acid dissociable group and theadjacent atom is cleaved by the action of acid; and

(ii) a group in which one of the bonds is cleaved by the action of acid,and then a decarboxylation reaction occurs, thereby cleaving the bondbetween the acid dis sociable group and the adjacent atom.

It is necessary that the acid dissociable group that constitutes theacid decomposable group is a group which exhibits a lower polarity thanthe polar group generated by the dissociation of the acid dissociablegroup. Thus, when the acid dissociable group is dissociated by theaction of acid, a polar group exhibiting a higher polarity than that ofthe acid dissociable group is generated, thereby increasing thepolarity. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, the solubility in an alkalideveloping solution changes and, the solubility in an organic developingsolution is relatively decreased.

The acid dissociable group is not particularly limited, and any of thegroups that have been conventionally proposed as acid dissociable groupsfor the base resins of chemically amplified resists can be used.

Examples of the acid dissociable group for protecting the carboxy groupor hydroxy group as a polar group include the acid dissociable grouprepresented by general formula (a1-r-1) shown below (hereafter, for thesake of convenience, sometimes referred to as “acetal-type aciddissociable group”).

In the formula, Ra′¹ and Ra′² represents a hydrogen atom or an alkylgroup; and Ra′³ represents a hydrocarbon group, provided that Ra′³ maybe bonded to Ra′¹ or Ra′²; and * represents a valence bond.

In formula (a1-r-1), as the lower alkyl group for Ra′¹ and Ra′², thesame lower alkyl groups as those described above the alkyl groups as thesubstituent which may be bonded to the carbon atom on the α-position ofthe aforementioned α-substituted alkylester can be used, although amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

The hydrocarbon group for Ra′³ is preferably an alkyl group of 1 to 20carbon atoms, more preferably an alkyl group of 1 to 10 carbon atoms,and still more preferably a linear or branched alkyl group. Specificexamples thereof include a methyl group, an ethyl group, a propyl group,an isopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, a neopentyl group, a1,1-dimethylethyl group, a 1,1-diethylpropyl group, a 2,2-dimethylpropylgroup and a 2,2-dimethylbutyl group.

In the case where Ra′³ represents a cyclic hydrocarbon group, the cyclichydrocarbon group may be aliphatic or aromatic, and may be polycyclic ormonocyclic. As the monocyclic aliphatic hydrocarbon group, a group inwhich 1 hydrogen atom has been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 8 carbon atoms, andspecific examples thereof include cyclopentane, cyclohexane andcyclooctane. As the polycyclic group, a group in which 1 hydrogen atomhas been removed from a polycycloalkane is preferable, and thepolycyclic group preferably has 7 to 12 carbon atoms. Examples of thepolycycloalkane include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane.

In the case where the hydrocarbon group is an aromatic hydrocarbongroup, examples of the aromatic ring contained in the aromatichydrocarbon group include aromatic hydrocarbon rings, such as benzene,biphenyl, fluorene, naphthalene, anthracene and phenanthrene; andaromatic hetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich 1 hydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group); and a group in which 1 hydrogen atom ofthe aforementioned aryl group has been substituted with an alkylenegroup (an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

In the case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, thecyclic group is preferably a 4 to 7-membered ring, and more preferably a4 to 6-membered ring. Specific examples of the cyclic group includetetrahydropyranyl group and tetrahydrofuranyl group.

Examples of the acid dissociable group for protecting the carboxy groupas a polar group include the acid dissociable group represented bygeneral formula (a1-r-2) shown below (hereafter, with respect to theacid dissociable group represented by the following formula (a1-r-2),the acid dissociable group constituted of alkyl groups is referred to as“tertiary ester-type acid dissociable group”).

In the formula, Ra′⁴ to Ra′⁶ each independently represents a hydrocarbongroup, provided that Ra′⁵ and Ra′⁶ may be mutually bonded to form aring; and * represents a valence bond.

As the hydrocarbon group for Ra′⁴ to Ra′⁶, the same groups as thosedescribed above for Ra′³ can be mentioned. Ra′⁴ is preferably an alkylgroup having from 1 to 5 carbon atoms. In the case where Ra′⁵ and Ra′⁶are mutually bonded to form a ring, a group represented by generalformula (a1-r2-1) shown below can be mentioned.

On the other hand, in the case where Ra′⁴ to Ra′⁶ are not mutuallybonded and independently represent a hydrocarbon group, the grouprepresented by general formula (a1-r2-2) shown below can be mentioned.

In the formulae, Ra′¹⁰ represents an alkyl group of 1 to 10 carbonatoms; Ra′¹¹ is a group which forms an aliphatic cyclic group togetherwith a carbon atom having Ra′¹⁰ bonded thereto; and Ra′¹² to Ra′¹⁴ eachindependently represents a hydrocarbon group; and * represents a valencebond.

In the formula (a1-r2-1), as the alkyl group of 1 to 10 carbon atoms forRa′¹⁰, the same groups as described above for the linear or branchedalkyl group for Ra′³ in the formula (a1-r-1) are preferable. In theformula (a1-r2-1), as the aliphatic cyclic group which is formed byRa′¹¹, the same groups as those described above for the cyclic alkylgroup for Ra′³ in the formula (a1-r-1) are preferable.

In the formula (a1-r2-2), it is preferable that Ra′¹² and Ra′¹⁴ eachindependently represents an alkyl group or 1 to 10 carbon atoms, and itis more preferable that the alkyl group is the same group as thedescribed above for the linear or branched alkyl group for Ra′³ in theformula (a1-r-1), it is still more preferable that the alkyl group is alinear alkyl group of 1 to 5 carbon atoms, and it is particularlypreferable that the alkyl group is a methyl group or an ethyl group.

In the formula (a1-r2-2), it is preferable that Ra′¹³ is the same groupas described above for the linear, branched or cyclic alkyl group forRa′³ in the formula (a1-r-1). Among these, the same cyclic alkyl groupas those describe above for Ra′³ is more preferable.

Specific examples of the formula (a1-r2-1) are shown below. In theformulae shown below, “*” represents a valence bond.

Specific examples of the formula (a1-r2-2) are shown below.

Examples of the acid dissociable group for protecting a hydroxy group asa polar group include the acid dissociable group represented by generalformula (a1-r-3) shown below (hereafter, referred to as “tertiaryalkyloxycarbonyl-type acid dissociable group”).

In the formula, Ra′⁷ to Ra′⁹ each independently represents an alkylgroup; and * represents a valence bond.

In the formula (a1-r-3), Ra′⁷ to Ra′⁹ is preferably an alkyl group of 1to 5 carbon atoms, and more preferably an alkyl group of 1 to 3 carbonatoms.

Further, the total number of carbon atoms within the alkyl group ispreferably 3 to 7, more preferably 3 to 5, and most preferably 3 or 4.

Examples of the structural unit (a1) include a structural unit derivedfrom an acrylate ester which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent andcontains an acid decomposable group which exhibits increased polarity bythe action of acid; a structural unit derived from hydroxystyrene or ahydroxystyrene derivative in which at least a part of the hydrogen atomof the hydroxy group is protected with a substituent containing an aciddecomposable group; and a structural unit derived from vinylbenzoic acidor a vinylbenzoic acid derivative in which at least a part of thehydrogen atom within —C(═O)—OH is protected with a substituentcontaining an acid decomposable group.

As the structural unit (a1), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

As the structural unit (a1), structural units represented by generalformula (a1-1) or (a1-2) shown below are preferable.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Va¹represents a divalent hydrocarbon group which may contain an ether bond,an urethane bond or an amide bond; each n_(a1) represents an integer of0 to 2; Ra¹ represents an acid dissociable group represented by theaforementioned formula (a1-r-1) or (a1-r-2); Wa¹ represents ahydrocarbon group having a valency of n_(a2)+1; n_(a2) represents aninteger of 1 to 3; and Ra² represents an acid dissociable grouprepresented by the aforementioned formula (a1-r-1) or (a1-r-3).

In general formula (a1-1), as the alkyl group of 1 to 5 carbon atoms forR, a linear or branched alkyl group of 1 to 5 carbon atoms ispreferable, and specific examples thereof include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl groupand a neopentyl group. The halogenated alkyl group of 1 to 5 carbonatoms represented by R is a group in which part or all of the hydrogenatoms of the aforementioned alkyl group of 1 to 5 carbon atoms have beensubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

The hydrocarbon group for Va¹ may be either an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. An “aliphatic hydrocarbon group”refers to a hydrocarbon group that has no aromaticity. The aliphatichydrocarbon group as the divalent hydrocarbon group for Va¹ may beeither saturated or unsaturated. In general, the aliphatic hydrocarbongroup is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

Further, as the group for Va¹, a group in which the aforementioneddivalent hydrocarbon group has been bonded via an ether bond, urethanebond or amide bond can be mentioned.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4,and most preferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which two hydrogenatoms have been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group, and a group inwhich the alicyclic group is interposed within the aforementioned linearor branched aliphatic hydrocarbon group, can be given. As the linear orbranched aliphatic hydrocarbon group, the same groups as those describedabove can be used.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic aliphatic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic group, a group in which two hydrogen atoms have been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring.

The aromatic hydrocarbon group as the divalent hydrocarbon group for Va¹preferably has 3 to 30 carbon atoms, more preferably 5 to 30, still morepreferably 5 to 20, still more preferably 6 to 15, and most preferably 6to 10. Here, the number of carbon atoms within a substituent(s) is notincluded in the number of carbon atoms of the aromatic hydrocarbongroup.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring (arylene group); and a group in which onehydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group) and one hydrogen atom has been substitutedwith an alkylene group (such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

In the aforementioned formula (a1-2), the hydrocarbon group for Wa¹having a valency of n_(a2)+1 may be either an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. The aliphatic cyclic grouprefers to a hydrocarbon group that has no aromaticity, and may be eithersaturated or unsaturated, but is preferably saturated. Examples of thealiphatic hydrocarbon group include a linear or branched aliphatichydrocarbon group, an aliphatic hydrocarbon group containing a ring inthe structure thereof, and a combination of the linear or branchedaliphatic hydrocarbon group and the aliphatic hydrocarbon groupcontaining a ring in the structure thereof. As the specific examplesthereof, the same groups as those described above for Va¹ in theaforementioned formula (a1-1) can be mentioned.

The valency of n_(a2)+1 is preferably divalent, trivalent ortetravalent, and divalent or trivalent is more preferable.

As the structural unit (a1-2), a structural unit represented by generalformula (a1-2-01) shown below is particularly desirable.

In the formula (a1-2-01), Ra² represents an acid dissociable grouprepresented by the aforementioned formula (a1-r-1) or (a1-r-3); n_(a)eis an integer of 1 to 3, preferably 1 or 2, and more preferably 1; c isan integer of 0 to 3, preferably 0 or 1, and more preferably 1; R is thesame as defined above.

Specific examples of the structural units (a1-1) and (a1-2) are shownbelow. In the formulae shown below, R^(α) represents a hydrogen atom, amethyl group or a trifluoromethyl group.

In the component (A), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A) is preferably 20 to 80 mol %, more preferably 20 to 75 mol %, andstill more preferably 25 to 70 mol %. By ensuring the lower limit,various lithography properties such as sensitivity, resolution and LWRare improved. On the other hand, when the amount of the structural unit(a1) is no more than the upper limit of the above-mentioned range, agood balance can be achieved with the other structural units.

(Structural Unit (a2))

In the present embodiment, the base component preferably contains astructural unit (a2) having an —SO₂— containing cyclic group, alactone-containing cyclic group, a carbonate-containing cyclic group orany other heterocyclic group.

When the component (A) is used for forming a resist film, the structuralunit (a2) containing an —SO₂— containing cyclic group, alactone-containing cyclic group, a carbonate-containing cyclic group orany other heterocyclic group is effective in improving the adhesionbetween the resist film and the substrate.

A structural unit (a1) (described later) which contains an —SO₂—containing cyclic group, a lactone-containing cyclic group, acarbonate-containing cyclic group or any other heterocyclic group fallsunder the definition of the structural unit (a2); however, such astructural unit is regarded as a structural unit (a1), and does not fallunder the definition of the structural unit (a2).

The structural unit (a2) is preferably a structural unit represented bygeneral formula (a2-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms, a halogenated alkyl group of 1 to 5 carbon atoms, ahydroxyalkyl group, an alkoxy group; Ya²¹ represents a single bond or adivalent linking group; La²¹ represents —O—, —COO—, —CON(R′)—, —OCO—,—CONHCO— or —CONHCS—; and R′ represents a hydrogen atom or a methylgroup, provided that, when La²¹ represents —O—, Ya²¹ does not represents—CO—; and Ra²¹ represents an —SO₂— containing cyclic group, alactone-containing cyclic group, a carbonate-containing cyclic group orany other heterocyclic group.

In formula (a2-1), Ra²¹ represents an —SO₂— containing cyclic group, alactone-containing cyclic group, a heterocyclic group or acarbonate-containing cyclic group.

The term “—SO₂— containing cyclic group” refers to a cyclic group whichcontains a ring containing —SO₂— within the ring skeleton thereof, morespecifically, a cyclic group in which the sulfur atom (S) of —SO₂— formspart of the ring skeleton. The ring containing —SO₂— within the ringskeleton thereof is counted as the first ring. A cyclic group in whichthe only ring structure is the ring that contains —SO₂— in the ringskeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings. The —SO₂— containingcyclic group may be either a monocyclic group or a polycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable. More specific examplesof the —SO₂— containing cyclic group include groups represented bygeneral formulas (a5-r-1) to (a5-r-4) shown below.

In the formulae, each Ra′⁵¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom or an alkyl group; A″ represents anoxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom; and n′ represents aninteger of 0 to 2.

In general formulae (a5-r-1) to (a5-r-4), A″ is the same as defined forA″ in general formulae (a2-r-1) to (a2-r-7) described later. The alkylgroup, alkoxy group, halogen atom, halogenated alkyl group, —COOR″,—OC(═O)R″ and hydroxyalkyl group for Ra′⁵′ are the same as defined forRa′²′ in general formulae (a2-r-1) to (a2-r-7) described later.

Specific examples of the groups represented by the aforementionedgeneral formulae (a5-r-1) to (a5-r-4) are shown below. In the formulaeshown below, “Ac” represents an acetyl group.

In the present embodiment, when the structural unit (a2) contains an—SO₂— containing cyclic group, there is no particular limitation as longas the acrylate ester monomer containing an —SO₂— containing cyclicgroup has a log P value of less than 1.2. Among these, a grouprepresented by the aforementioned general formula (a5-r-1) ispreferable, at least one member selected from the group consisting ofgroups represented by the aforementioned chemical formulas (r-s1-1-1),(r-s1-1-18), (r-s1-3-1) and (r-s1-4-1) is more preferable, and a grouprepresented by chemical formula (r-s1-1-1) is most preferable.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings. The lactone-containing cyclic groupmay be either a monocyclic group or a polycyclic group.

As the lactone-containing cyclic group, there is no particularlimitation, and an arbitrary group may be used. Specific examplesinclude groups represented by general formulae (a2-r-1) to (a2-r-7)shown below. Hereinbelow, “*” represents a valence bond.

In the formulae, each Ra′²¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom or an alkyl group; A″ represents anoxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom; n′ represents aninteger of 0 to 2; and m′ represents 0 or 1.

In general formulae (a2-r-1) to (a2-r-7) above, A″ represents an oxygenatom (—O—), a sulfur atom (—S—) or an alkylene group of 1 to 5 carbonatoms which may contain an oxygen atom or a sulfur atom. As the alkylenegroup of 1 to 5 carbon atoms for A″, a linear or branched alkylene groupis preferable, and examples thereof include a methylene group, anethylene group, an n-propylene group and an isopropylene group. Examplesof alkylene groups that contain an oxygen atom or a sulfur atom includethe aforementioned alkylene groups in which —O— or —S— is bonded to theterminal of the alkylene group or present between the carbon atoms ofthe alkylene group. Specific examples of such alkylene groups include—O—CH₂—, —CH₂—O—CH₂—, —S—CH₂— and —CH₂—S—CH₂—. As A″, an alkylene groupof 1 to 5 carbon atoms or —O— is preferable, more preferably an alkylenegroup of 1 to 5 carbon atoms, and most preferably a methylene group.Each Ra′²¹ independently represents an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, —COOR″, —OC(═O)R″, ahydroxyalkyl group or a cyano group.

The alkyl group for Ra′²¹ is preferably an alkyl group of 1 to 5 carbonatoms.

The alkoxy group for Ra′²¹ is preferably an alkoxy group of 1 to 6carbon atoms.

The alkoxy group is preferably a linear or branched alkoxy group.Specific examples of the alkoxy groups include the aforementioned alkylgroups for Ra′²¹ having an oxygen atom (—O—) bonded thereto.

As examples of the halogen atom for Ra′²¹, a fluorine atom, chlorineatom, bromine atom and iodine atom can be given. Among these, a fluorineatom is preferable.

Examples of the halogenated alkyl group for Ra′²¹ include groups inwhich part or all of the hydrogen atoms within the aforementioned alkylgroup for Ra′²¹ has been substituted with the aforementioned halogenatoms. As the halogenated alkyl group, a fluorinated alkyl group ispreferable, and a perfluoroalkyl group is particularly desirable.

Specific examples of the groups represented by the aforementionedgeneral formulae (a2-r-1) to (a2-r-7) are shown below.

In the present embodiment, the structural unit (a2) preferably has agroup represented by the aforementioned formula (a2-r-1) or (a2-r-2),and more preferably a group represented by the aforementioned chemicalformula (r-1c-1-1) or (r-1c-2-7).

The term “carbonate-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)—O— structure (carbonate ring).The term “carbonate ring” refers to a single ring containing a—O—C(═O)—O— structure, and this ring is counted as the first ring. Acarbonate-containing cyclic group in which the only ring structure isthe carbonate ring is referred to as a monocyclic group, and groupscontaining other ring structures are described as polycyclic groupsregardless of the structure of the other rings. The carbonate-containingcyclic group may be either a monocyclic group or a polycyclic group.

Specific examples include groups represented by general formulas(ax3-r-1) to (ax3-r-3) shown below.

In the formulae, each Ra′^(x31) independently represents a hydrogenatom, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group ora cyano group; R″ represents a hydrogen atom or an alkyl group; A″represents an oxygen atom, a sulfur atom or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom; and q′represents 0 or 1.

In general formulae (ax3-r-1) to (ax3-r-3), specific examples of A″ isthe same as defined for A″ in general formulae (a2-r-1) to (a2-r-7).Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′^(x31)include the same groups as those described above in the explanation ofRa′²¹ in the general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (ax3-r-1) to (ax3-r-3) are shown below.

A “heterocyclic group” refers to a cyclic group containing, in additionto carbon, 1 or more atoms other than carbon. Examples of theheterocyclic group include heterocyclic groups represented by theaforementioned formulae (r-hr-1) to (r-hr-16) and nitrogen-containingheterocyclic groups. Examples of the nitrogen-containing heterocyclicgroups include cycloalkyl groups of 3 to 8 carbon atoms which may besubstituted with 1 or 2 oxo groups. Preferable examples of thecycloalkyl group include 2,5-dioxopyrrolidine and 2,6-dioxopiperidine.

As the structural unit (a2) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the component (A1) contains the structural unit (a2), the amount ofthe structural unit (a2) based on the combined total of all structuralunits constituting the component (A) is preferably 1 to 80 mol %, morepreferably 5 to 70 mol %, still more preferably 10 to 65 mol %, and mostpreferably 10 to 60 mol %. When the amount of the structural unit (a2)is at least as large as the lower limit of the above-mentioned range,the effect of using the structural unit (a2) can be satisfactorilyachieved. On the other hand, when the amount of the structural unit (a2)is no more than the upper limit of the above-mentioned range, a goodbalance can be achieved with the other structural units, and variouslithography properties and pattern shape can be improved.

(Structural Unit (a3))

The structural unit (a3) is a structural unit containing a polargroup-containing aliphatic hydrocarbon group (provided that thestructural units that fall under the definition of structural units (a1)and (a2) are excluded).

When the component (A1) includes the structural unit (a3), it ispresumed that the hydrophilicity of the component (A1) is enhanced,thereby contributing to improvement in resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups can be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

As the structural unit (a3), there is no particular limitation as longas it is a structural unit containing a polar group-containing aliphatichydrocarbon group, and an arbitrary structural unit may be used.

The structural unit (a3) is preferably a structural unit derived from anacrylate ester which may have the hydrogen atom bonded to the carbonatom on the α-position substituted with a substituent and contains apolar group-containing aliphatic hydrocarbon group.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

The amount of the structural unit (a3) within the component (A1) basedon the combined total of all structural units constituting the component(A1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a3) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a3) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units.

The component (A1) may also include a structural unit (a4) which isother than the above-mentioned structural units (a1), (a2) and (a3).

(Structural Unit (a4))

The structural unit (a4) is a structural unit containing an acidnon-dissociable cyclic group. When the component (A1) includes thestructural unit (a4), dry etching resistance of the resist pattern to beformed is improved. Further, the hydrophobicity of the component (A1) isfurther improved. Increase in the hydrophobicity contributes toimprovement in terms of resolution, shape of the resist pattern and thelike, particularly in an organic solvent developing process.

An “acid non-dissociable, aliphatic cyclic group” in the structural unit(a4) refers to a cyclic group which is not dissociated by the action ofacid generated from the component (B) described later upon exposure, andremains in the structural unit.

As the structural unit (a4), a structural unit which contains anon-acid-dissociable aliphatic cyclic group, and is also derived from anacrylate ester is preferable. Examples of this cyclic group include thesame groups as those described above in relation to the aforementionedstructural unit (a1), and any of the multitude of conventional groupsused within the resin component of resist compositions for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecyl group, adamantylgroup, tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable. These polycyclic groups may be substituted witha linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-7) shown below.

In the formulae, R^(α) represents a hydrogen atom, a methyl group or atrifluoromethyl group.

As the structural unit (a4) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the structural unit (a4) is included in the component (A1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

The component (A1) is preferably a copolymer having the structural units(a1), (a2) and (a3).

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN) or dimethyl2,2′-azobis(isobutyrate).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

In the present invention, the weight average molecular weight (Mw) (thepolystyrene equivalent value determined by gel permeationchromatography) of the component (A1) is not particularly limited, butis preferably 1,000 to 50,000, more preferably 1,500 to 30,000, and mostpreferably 2,000 to 20,000. When the weight average molecular weight isno more than the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the weight average molecular weight is at least aslarge as the lower limit of the above-mentioned range, dry etchingresistance and the cross-sectional shape of the resist pattern becomessatisfactory.

As the component (A1), one kind of compound may be used alone, or two ormore kinds of compounds may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, various lithography propertiesare improved.

In the present embodiment, as the component (A), one kind of compoundmay be used, or two or more kinds of compounds may be used incombination.

In the present embodiment, the amount of the component (A) can beappropriately adjusted depending on the thickness of the resist film tobe formed, and the like.

<Acid Generator Component; Component (B)>

In the present invention, the resist composition includes an acidgenerator component (B) (hereafter, referred to as “component (B)”)which generates acid upon exposure. The component (B) includes at leastone acid generator (B1) represented by general formula (b1) shown below,at least one acid generator (B2) represented by general formula (b2)shown below, and at least one acid generator (B3) represented by generalformula (b3) shown below.[Chemical Formula 27]R¹—Y¹—(CF₂)_(n)—SO₃ ⁻M₁ ⁺  (b1)R²—(CH₂)_(m)—SO₃ ⁻M₂ ⁺  (b2)R³—COO⁻M₃ ⁺  (b3)

In the formulae, R¹ to R³ each independently represents a cyclic groupwhich may have a substituent, a chain alkyl group, or a chain alkenylgroup; Y¹ represents a single bond or a divalent linking groupcontaining an oxygen atom; M₁ ⁺ to M₃ ⁺ represents a monovalent organiccation; n represents an integer of 1 to 4; m represents an integer of 0to 4; provided that, when m is 0, the carbon atom adjacent to the sulfuratom within R² has no fluorine atom bonded thereto.

[Component (B1)]

Anion Moiety

In formula (b1), R¹ represents a cyclic group which may have asubstituent, a chain alkyl group, or a chain alkenyl group.

(Cyclic Group which May have a Substituent for R¹)

The cyclic group is preferably a cyclic hydrocarbon group, and thecyclic hydrocarbon group may be either an aromatic hydrocarbon group oran aliphatic hydrocarbon group.

As the aromatic hydrocarbon group for R¹, groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring described abovein relation to the divalent aromatic hydrocarbon group for Va¹ in theformula (a1-1) or an aromatic compound containing two or more aromaticring can be mentioned, and a phenyl group or a naphthyl group ispreferable.

As the cyclic aliphatic hydrocarbon group for R¹, groups in which onehydrogen atom has been removed from a monocycloalkane or apolycycloalkane exemplified above in the explanation of the divalentaliphatic hydrocarbon group for Va¹ in the formula (a1-1) can bementioned, and an adamantyl group or a norbornyl group is preferable.

Further, the cyclic hydrocarbon group for R¹ may contain a hetero atomlike as a heterocycle, and specific examples thereof includelactone-containing cyclic groups represented by the aforementionedgeneral formulas (a2-r-1) to (a2-r-7), —SO₂— containing cyclic groupsrepresented by the aforementioned formulas (a5-r-1) to (a5-r-4) andheterocyclic groups represented by formulae (r-hr-1) to (r-hr-16) shownbelow.

As the substituent for the cyclic hydrocarbon group for R¹, an alkylgroup, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group or the like may be used.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Example of the aforementioned halogenated alkyl group includes a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

(Chain Alkyl Group which May have a Substituent for R¹)

The chain alkyl group for R¹ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, morepreferably 1 to 15, and most preferably 1 to 10. Specific examplesinclude a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonylgroup, a decyl group, an undecyl group, a dodecyl group, a tridecylgroup, an isotridecyl group, a tetradecyl group, a pentadecyl group, ahexadecyl group, an isohexadecyl group, a heptadecyl group, an octadecylgroup, a nonadecyl group, an icosyl group, a henicosyl group and adocosyl group.

The branched alkyl group preferably has 3 to 20 carbon atoms, morepreferably 3 to 15, and most preferably 3 to 10. Specific examplesinclude a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropylgroup, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutylgroup, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentylgroup, a 2-methylpentyl group, a 3-methylpentyl group and a4-methylpentyl group.

(Chain Alkenyl Group which May have a Substituent for R¹)

The chain alkenyl group for R¹ may be linear or branched, and preferablyhas 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, stillmore preferably 2 to 4 carbon atoms, and most preferably 3 carbon atoms.Examples of linear alkenyl groups include a vinyl group, a propenylgroup (an allyl group) and a butynyl group. Examples of branched alkenylgroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the chain alkenyl group, apropenyl group is particularly desirable.

As the substituent for the chain alkyl group or alkenyl group for R¹, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup, a carbonyl group, a nitro group, an amino group, a cyclic groupfor R¹ or the like may be used.

Among these examples, as R¹, a cyclic group which may have a substituentis preferable, and a cyclic hydrocarbon group which may have asubstituent is more preferable. Specifically, a phenyl group, a naphthylgroup, a group in which one or more hydrogen atoms have been removedfrom a polycycloalkane, a lactone-containing cyclic group represented byany one of the aforementioned formula (a2-r-1) to (a2-r-7), and an —SO₂—containing cyclic group represented by any one of the aforementionedformula (a5-r-1) to (a5-r-4).

In formula (b1), Y¹ represents a single bond or a divalent linking groupcontaining an oxygen atom.

In the case where Y¹ is a divalent linking group containing an oxygenatom, may contain an atom other than an oxygen atom. Examples of atomsother than an oxygen atom include a carbon atom, a hydrogen atom, asulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amido bond (—C(═O)—NH—), a carbonyl group(—C(═O)—) and a carbonate bond (—O—C(═O)—O—); and combinations of theaforementioned non-hydrocarbon, hetero atom-containing linking groupswith an alkylene group. Furthermore, the combinations may have asulfonyl group (—SO₂—) bonded thereto. As the combination, the linkinggroup represented by formulas (y-a1-1) to (y-a1-7) shown below can bementioned.

In the formulae, V′¹⁰¹ represents a single bond or an alkylene group of1 to 5 carbon atoms; V′¹⁰² represents a divalent saturated hydrocarbongroup of 1 to 30 carbon atoms.

The divalent saturated hydrocarbon group for V′¹⁰² is preferably analkylene group of 1 to 30 carbon atoms.

The alkylene group for V′¹⁰¹ and V′¹⁰² may be a linear alkylene group ora branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group for V′¹⁰¹ and V′¹⁰² include amethylene group [—CH₂—]; an alkylmethylene group, such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and—C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group, suchas —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; analkyltrimethylene group, such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group,such as —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylenegroup [—CH₂CH₂CH₂CH₂CH₂—].

Further, part of methylene group within the alkylene group for V′¹⁰¹ andV′¹⁰² may be substituted with a divalent aliphatic cyclic group of 5 to10 carbon atoms. The aliphatic cyclic group is preferably a divalentgroup in which one hydrogen atom has been removed from the cyclicaliphatic hydrocarbon group for Ra′³ in the aforementioned formula(a1-r-1), and a cyclohexylene group, 1,5-adamantylene group or2,6-adamantylene group is preferable.

Y¹ is preferably a divalent linking group containing an ether bond or anester bond, and groups represented by the aforementioned formulas(y-a1-1) to (y-a1-5) are preferable.

Specific examples of the anion moiety of the component (B1) include, inthe case where Y¹ is a single bond, a fluorinated alkylsulfonate anion,such as a trifluoromethanesulfonate anion or a perfluorobutanesulfonateanion; and in the case where Y¹ is a divalent linking group containingan oxygen atom, an anion represented by any one of general formulae(an-1) to (an-3) shown below.

In the formulae, R″¹⁰¹ represents an aliphatic cyclic group which mayhave a substituent, a group represented by any one of the aforementionedformulae (r-hr-1) to (r-hr-6) or a chain-like alkyl group which may havea substituent; R″¹⁰² represents an aliphatic cyclic group which may havea substituent, a lactone-containing cyclic group represented by any oneof the aforementioned general formulae (a2-r-1) to (a2-r-7) or an —SO₂—containing cyclic group represented by any one of the aforementionedgeneral formulae (a5-r-1) to (a5-r-4); R″¹⁰³ represents an aromaticcyclic group which may have a substituent, an aliphatic cyclic groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent; V″¹⁰¹ represents a fluorinated alkylene group; L″¹⁰¹represents —C(═O)— or —SO₂—; v″ represents an integer of 0 to 3; q″represents an integer of 1 to 20; and n″ represents 0 or 1.

As the aliphatic cyclic group for R″¹⁰¹, R″¹⁰² and R″¹⁰³ which may havea substituent, the same groups as the cyclic aliphatic hydrocarbon groupfor R¹ described above are preferable. As the substituent, the samegroups as those described above for substituting the cyclic aliphatichydrocarbon group for R¹ can be mentioned.

As the aromatic cyclic group for R″¹⁰³ which may have a substituent, thesame groups as the aromatic hydrocarbon group for the cyclic hydrocarbongroup represented by R¹ described above are preferable. The substituentis the same as defined for the substituent for the aromatic hydrocarbongroup represented by R¹.

As the chain-like alkyl group for R″¹⁰¹ which may have a substituent,the same groups as those described above for R¹ are preferable. As thechain-like alkenyl group for R″¹⁰³ which may have a substituent, thesame groups as those described above for R′¹⁰¹ are preferable. V″¹⁰¹ ispreferably a fluorinated alkylene group of 1 to 3 carbon atoms, and mostpreferably —CF₂—, —CF₂CF₂—, —CH₂CF₂—, —CF(CF₃)CF₂— or —CH(CF₃)CF₂—.

Specific examples of preferable anion moieties for the component (B1)are shown below.

Cation Moiety

In formula (b1), M₁ ⁺ represents a monovalent organic cation.

The organic cation for M₁ ⁺ is not particularly limited. As the organiccation, sulfonium cation or an iodonium cation is preferable, and acation represented by any one of general formulae (ca-1) to (ca-4) shownbelow is preferable.

In the formulae, R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² each independentlyrepresents an aryl group, an alkyl group or an alkenyl group, providedthat two of R²⁰¹ to R²⁰³, R²⁰⁶ and, R²⁰⁷, or R²¹¹ and R²¹² may bemutually bonded to form a ring with the sulfur atom; R²⁰⁸ and R²⁰⁹ eachindependently represents a hydrogen atom or an alkyl group of 1 to 5carbon atoms; R²¹⁰ represents an aryl group which may have asubstituent, an alkyl group which may have a substituent, an alkenylgroup which may have a substituent or an —SO₂— containing cyclic groupwhich may have a substituent; L²⁰¹ represents —C(═O)— or —C(═O)—O—; Y²⁰¹each independently represents an arylene group, an alkylene group or analkenylene group; x represents 1 or 2; and W²⁰¹ represents a linkinggroup having a valency of (x+1).

As the aryl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹², an unsubstituted arylgroup of 6 to 20 carbon atoms can be mentioned, and a phenyl group or anaphthyl group is preferable.

The alkyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² is preferably achain-like or cyclic alkyl group having 1 to 30 carbon atoms.

The alkenyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² preferably has 2 to 10carbon atoms.

Specific examples of the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹²may have include an alkyl group, a halogen atom, a halogenated alkylgroup, a carbonyl group, a cyano group, an amino group, an aryl group,an arylthio group and groups represented by formulae (ca-r-1) to(ca-r-7) shown below.

The aryl group within the arylthio group as the substituent is the sameas defined for IV, and specific examples include a phenylthio group anda biphenylthio group.

In the formulae, R′²⁰¹ each independently represents a hydrogen atom, acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent.

As the cyclic group which may have a substituent, the chain-like alkylgroup which may have a substituent and the chain-like alkenyl groupwhich may have a substituent for R′²⁰¹, the same groups as thosedescribed above for IV can be mentioned.

As the cyclic group which may have a substituent and chain-like alkylgroup which may have a substituent, the same groups as those describedabove for the acid dissociable group represented by the aforementionedformula (a1-r-2) can be also mentioned.

When R²⁰¹ to R²⁰³, R²⁰⁶, R²⁰⁷, R²¹¹ and R²¹² are mutually bonded to forma ring with the sulfur atom, these groups may be mutually bonded via ahetero atom such as a sulfur atom, an oxygen atom or a nitrogen atom, ora functional group such as a carbonyl group, —SO—, —SO₂—, —SO₃—, —COO—,—CONH— or —N(R_(N))— (wherein R_(N) represents an alkyl group of 1 to 5carbon atoms). The ring containing the sulfur atom in the skeletonthereof is preferably a 3 to 10-membered ring, and most preferably a 5to 7-membered ring. Specific examples of the ring formed include athiophene ring, a thiazole ring, a benzothiophene ring, a thianthrenering, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthenering, a thioxanthone ring, a phenoxathiin ring, a tetrahydrothiopheniumring, and a tetrahydrothiopyranium ring.

R²⁰⁸ and R²⁰⁹ each independently represents a hydrogen atom or an alkylgroup of 1 to 5 carbon atoms, preferably a hydrogen atom or an alkylgroup of 1 to 3 carbon atoms, and when R²⁰⁸ and R²⁰⁹ each represents analkyl group, R²⁰⁸ and R²⁰⁹ may be mutually bonded to form a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkylgroup which may have a substituent, an alkenyl group which may have asubstituent, or an —SO₂— containing cyclic group which may have asubstituent.

Examples of the aryl group for R²¹⁰ include an unsubstituted aryl groupof 6 to 20 carbon atoms, and a phenyl group or a naphthyl group ispreferable.

As the alkyl group for R²¹⁰, a chain-like or cyclic alkyl group having 1to 30 carbon atoms is preferable.

The alkenyl group for R²¹⁰ preferably has 2 to 10 carbon atoms.

As the —SO₂— containing cyclic group for R²¹⁰ which may have asubstituent, the same “—SO₂— containing cyclic group” as those describedabove for Ra²¹ in the aforementioned general formula (a2-1) can bementioned, and the group represented by the aforementioned generalformula (a5-r-1) is preferable.

Each Y²⁰¹ independently represents an arylene group, an alkylene groupor an alkenylene group.

Examples of the arylene group for Y²⁰¹ include groups in which onehydrogen atom has been removed from an aryl group given as an example ofthe aromatic hydrocarbon group for R¹ in the aforementioned formula(b1).

The alkylene group and the alkenylene group for Y²⁰¹ is the same asdefined for the aliphatic hydrocarbon group as the divalent linkinggroup represented by Va¹ in the aforementioned general formula (a1-1).

In the formula (ca-4), x represents 1 or 2.

W²⁰¹ represents a linking group having a valency of (x+1), i.e., adivalent or trivalent linking group.

As the divalent linking group for W²⁰¹, a divalent hydrocarbon groupwhich may have a substituent is preferable, and as examples thereof, thesame hydrocarbon groups as those described above for Ya²¹ in the generalformula (a2-1) can be mentioned. The divalent linking group for W²⁰¹ maybe linear, branched or cyclic, and cyclic is more preferable. Amongthese, an arylene group having two carbonyl groups, each bonded to theterminal thereof is preferable. Examples of the arylene group include aphenylene group and a naphthylene group, and a phenylene group isparticularly desirable.

As the trivalent linking group for W²⁰¹, a group in which one hydrogenatom has been removed from the aforementioned divalent linking group forW²⁰¹ and a group in which the divalent linking group has been bonded toanother divalent linking group can be mentioned. The trivalent linkinggroup for W²⁰¹ is preferably a group in which 2 carbonyl groups arebonded to an arylene group.

Specific examples of preferable cations represented by formula (ca-1)include cations represented by formulae (ca-1-1) to (ca-1-65) shownbelow.

In the formulae, g1, g2 and g3 represent recurring numbers, wherein g1is an integer of 1 to 5, g2 is an integer of 0 to 20, and g3 is aninteger of 0 to 20.

In the formulae, R″²⁰¹ represents a hydrogen atom or a substituent, andas the substituent, the same groups as those described above forsubstituting R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² can be mentioned.

Specific examples of preferable cations represented by formula (ca-3)include cations represented by formulae (ca-3-1) to (ca-3-6) shownbelow.

Specific examples of preferable cations represented by formula (ca-4)include cations represented by formulae (ca-4-1) and (ca-4-2) shownbelow.

Among these examples, as the cation moiety, a cation represented bygeneral formula (ca-1) is preferable, and a cation represented by any offormulae (ca-1-1) to (ca-1-65) is more preferable.

As the component (B1), one kind of compound may be used, or two or morekinds of compounds may be used in combination.

[Component (B2)]

Anion Moiety

In formula (b2), R² represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent, or achain alkenyl group which may have a substituent, and is the same asdefined for R¹ in the aforementioned formula (b1).

However, when m is 0, the carbon atom adjacent to the sulfur atom withinR² has no fluorine atom bonded thereto (R² is not substituted withfluorine). As a result, the anion moiety of the component (B2) becomesan appropriately weak acidic anion.

As R², an aliphatic cyclic group which may have a substituent ispreferable, and a group in which one or more hydrogen atoms have beenremoved from adamantane, norbornane, isobornane, tricyclodecane,tetracyclododecane or camphor (which may have a substituent) is morepreferable.

The hydrocarbon group for R² may have a substituent. As the substituent,the same groups as those described above for substituting thehydrocarbon group (e.g., aromatic hydrocarbon group, aliphatichydrocarbon group) for R³ in the formula (b3) described later may bementioned.

Specific examples of preferable anion moieties for the component (B2)are shown below.

Cation Moiety

In formula (b2), M₂ ⁺ represents a monovalent organic cation, and is thesame as defined for M₁+ in the aforementioned formula (b1).

As the component (B2), one kind of compound may be used, or two or morekinds of compounds may be used in combination.

[Component (B3)]

Anion Moiety

In formula (b3), R³ represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent, or achain alkenyl group which may have a substituent, and is the same asdefined for IV in the aforementioned formula (b1).

Among these, as the group for R³, an aromatic hydrocarbon group whichmay have a substituent, an aliphatic cyclic group which may have asubstituent and a chain-like hydrocarbon group which may have asubstituent are preferable. Examples of the substituent for these groupsinclude a hydroxy group, an oxo group, an alkyl group, an aryl group, afluorine atom, a fluorinated alkyl group, a lactone-containing cyclicgroup represented by any one of the aforementioned formulae (a2-r-1) to(a2-r-7), an ether bond, an ester bond, and a combination thereof. Inthe case where an ether bond or an ester bond is included as thesubstituent, the substituent may be bonded via an alkylene group, and alinking group represented by any one of the aforementioned formulae(y-a1-1) to (y-a1-5) is preferable as the substituent.

The aromatic hydrocarbon group is preferably a phenyl group or anaphthyl group.

Examples of the aliphatic cyclic group include groups in which one ormore hydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane.

As the chain hydrocarbon group, a chain alkyl group is preferable. Thechain-like alkyl group preferably has 1 to 10 carbon atoms, and specificexamples thereof include a linear alkyl group such as a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup, a heptyl group, an octyl group, a nonyl or a decyl group, and abranched alkyl group such as a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup or a 4-methylpentyl group.

In the case where the chain-like alkyl group is a fluorinated alkylgroup having a fluorine atom or a fluorinated alkyl group, thefluorinated alkyl group preferably has 1 to 11 carbon atoms, morepreferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbonatoms. The fluorinated alkyl group may contain an atom other thanfluorine. Examples of the atom other than fluorine include an oxygenatom, a carbon atom, a hydrogen atom, a sulfur atom and a nitrogen atom.

As R³, a fluorinated alkyl group in which part or all of the hydrogenatoms constituting a linear alkyl group have been substituted withfluorine atom(s) is preferable, and a fluorinated alkyl group in whichall of the hydrogen atoms constituting a linear alkyl group have beensubstituted with fluorine atoms (i.e., a linear perfluoroalkyl group) ismore preferable.

Specific examples of preferable anion moieties for the component (B3)are shown below.

Cation Moiety

In formula (b3), M₃ ⁺ represents a monovalent organic cation, and is thesame as defined for M₁ ⁺ in the aforementioned formula (b1).

As the component (B3), one kind of compound may be used, or two or morekinds of compounds may be used in combination.

In the resist composition, the amount of the component (B), relative to100 parts by weight of the component (A) is preferably from 0.5 to 60parts by weight, more preferably from 1 to 50 parts by weight, and mostpreferably from 1 to 40 parts by weight.

When the amount of the component (B) is within the above-mentionedrange, formation of a resist pattern can be satisfactorily performed.Further, by virtue of the above-mentioned range, when each of thecomponents is dissolved in an organic solvent, a homogeneous solutionmay be more reliably obtained and the storage stability of the resistcomposition becomes satisfactory.

Moreover, the component (B2) and the component (B3) exhibit a quenchingeffect of trapping acid generated from an acid generator or the like byion exchange reaction.

<Photoreactive Quencher Component; Component (D)>

The resist composition of the present embodiment may further contain aphotoreactive quencher component (hereafter, referred to as “component(D)”).

The component (D) functions as an acid diffusion control agent, i.e., aquencher which traps the acid generated from the component (B) and thelike upon exposure.

In the present invention, as the component (D), a nitrogen-containingorganic compound is preferable.

As the component (D), an aliphatic amine, in particular, a secondaryaliphatic amine or tertiary aliphatic amine is preferable.

An aliphatic amine is an amine having one or more aliphatic groups, andthe aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines Specific examples ofalkylamines and alkylalcoholamines include monoalkylamines such asn-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, andn-decylamine; dialkylamines such as diethylamine, di-n-propylamine,di-n-heptylamine, di-n-octylamine, and dicyclohexylamine; trialkylaminessuch as trimethylamine, triethylamine, tri-n-propylamine,tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine,tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decylamine,and tri-n-dodecylamine; and alkyl alcohol amines such as diethanolamine,triethanolamine, diisopropanolamine, triisopropanolamine,di-n-octanolamine, and tri-n-octanolamine. Among these, trialkylaminesof 5 to 10 carbon atoms are preferable, and tri-n-pentylamine andtri-n-octylamine are particularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanolaminetriacetate, and triethanolamine triacetate is preferable.

Further, as the component (D), an aromatic amine may be used.

Examples of aromatic amines include aniline, pyridine,4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole andderivatives thereof, as well as diphenylamine, triphenylamine,tribenzylamine, 2,6-diisopropylaniline andN-tert-butoxycarbonylpyrrolidine.

As the component (D), one type of compound may be used alone, or two ormore types may be used in combination.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

As the component (D), one type of compound may be used, or two or moretypes of compounds may be used in combination.

In the present embodiment, when the resist composition contains thecomponent (D), the amount of the component (D) relative to 100 parts byweight of the component (A) is preferably within a range from 0.1 to 15parts by weight, more preferably from 0.3 to 12 parts by weight, andstill more preferably from 0.5 to 12 parts by weight. When the amount ofthe component (D) is at least as large as the lower limit of theabove-mentioned range, various lithography properties (such as LWR) ofthe resist composition are improved. Further, a resist pattern having anexcellent shape can be obtained. On the other hand, when the amount ofthe component (D) is no more than the upper limit of the above-mentionedrange, sensitivity can be maintained at a satisfactory level, andthrough-put becomes excellent.

<Optional Components>

[Component (E)]

In the present invention, in the resist composition, for preventing anydeterioration in sensitivity, and improving the resist pattern shape andthe post exposure stability of the latent image formed by thepattern-wise exposure of the resist layer, at least one compound (E)(hereafter referred to as the component (E)) selected from the groupconsisting of an organic carboxylic acid, or a phosphorus oxo acid orderivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid estersand phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

[Component (F)]

In the present invention, the resist composition of the presentinvention may contain a fluorine additive (hereafter, referred to as“component (F)”) for imparting water repellency to the resist film.

As the component (F), for example, a fluorine-containing polymericcompound described in Japanese Unexamined Patent Application, FirstPublication No. 2010-002870, Japanese Unexamined Patent Application,First Publication No. 2010-032994, Japanese Unexamined PatentApplication, First Publication No. 2010-277043, Japanese UnexaminedPatent Application, First Publication No. 2011-13569, and JapaneseUnexamined Patent Application, First Publication No. 2011-128226 can beused.

Specific examples of the component (F) include polymers having astructural unit (f1) represented by general formula (f1-1) shown below.As the polymer, a polymer (homopolymer) consisting of a structural unit(f1) represented by formula (f1-1) shown below; a copolymer of astructural unit (f1) represented by formula (f1-1) shown below and theaforementioned structural unit (a1); and a copolymer of a structuralunit (f1) represented by formula (f1-1) shown below, a structural unitderived from acrylic acid or methacrylic acid and the aforementionedstructural unit (a1) are preferable. As the structural unit (a1) to becopolymerized with a structural unit (f1) represented by formula (f1-1)shown below, a structural unit derived from1-ethyl-1-cyclooctyl(meth)acrylate or a structural unit represented bythe aforementioned formula (a1-2-01) is preferable.

In the formula, R is the same as defined above; Rf¹⁰² and Rf¹⁰³ eachindependently represents a hydrogen atom, a halogen atom, an alkyl groupof 1 to 5 carbon atoms, or a halogenated alkyl group of 1 to 5 carbonatoms, provided that Rf¹⁰² and Rf¹⁰³ may be the same or different; nf¹represents an integer of 1 to 5; and Rf¹⁰¹ represents an organic groupcontaining a fluorine atom.

In formula (f1-1), R is the same as defined above. As R, a hydrogen atomor a methyl group is preferable.

In formula (f1-1), examples of the halogen atom for Rf¹⁰² and Rf¹⁰³include a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable. Examples of thealkyl group of 1 to 5 carbon atoms for Rf¹⁰² and Rf¹⁰³ include the samealkyl group of 1 to 5 carbon atoms as those described above for R, and amethyl group or an ethyl group is preferable. Specific examples of thehalogenated alkyl group of 1 to 5 carbon atoms represented by Rf¹⁰² orRf¹⁰³ include groups in which part or all of the hydrogen atoms of theaforementioned alkyl groups of 1 to 5 carbon atoms have been substitutedwith halogen atoms. Examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is particularly desirable. Among these, as Rf¹⁰² and Rf¹⁰³, ahydrogen atom, a fluorine atom or an alkyl group of 1 to 5 carbon atomsis preferable, and a hydrogen atom, a fluorine atom, a methyl group oran ethyl group is more preferable.

In formula (f1-1), nf¹ represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2.

In formula (f1-1), Rf¹⁰¹ represents an organic group containing afluorine atom, and is preferably a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branchedor cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to15 carbon atoms, and most preferably 1 to 10 carbon atoms.

It is preferable that the hydrocarbon group having a fluorine atom has25% or more of the hydrogen atoms within the hydrocarbon groupfluorinated, more preferably 50% or more, and most preferably 60% ormore, as the hydrophobicity of the resist film during immersion exposureis enhanced.

Among these, as Rf¹⁰¹, a fluorinated hydrocarbon group of 1 to 5 carbonatoms is preferable, and a methyl group, —CH₂—CF₃, —CH₂—CF₂—CF₃,—CH(CF₃)₂, —CH₂—CH₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ are mostpreferable.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (F)is preferably 1,000 to 50,000, more preferably 5,000 to 40,000, and mostpreferably 10,000 to 30,000. When the weight average molecular weight isno more than the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the weight average molecular weight is at least aslarge as the lower limit of the above-mentioned range, dry etchingresistance and the cross-sectional shape of the resist pattern becomessatisfactory.

Further, the dispersity (Mw/Mn) of the component (F) is preferably 1.0to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

As the component (F), one type may be used alone, or two or more typesmay be used in combination.

The component (F) is generally used in an amount within a range from 0.5to 10 parts by weight, relative to 100 parts by weight of the component(A).

In the present invention, if desired, other miscible additives can alsobe added to the resist composition. Examples of such miscible additivesinclude additive resins for improving the performance of the resistfilm, dissolution inhibitors, plasticizers, stabilizers, colorants,halation prevention agents, and dyes.

[Component (S)]

In the present invention, the resist composition can be prepared bydissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone (MEK), cyclohexanone, methyl-n-pentylketone (2-heptanone), and methyl isopentyl ketone; polyhydric alcohols,such as ethylene glycol, diethylene glycol, propylene glycol anddipropylene glycol; compounds having an ester bond, such as ethyleneglycol monoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; aromatic organic solventssuch as anisole, ethylbenzylether, cresylmethylether, diphenylether,dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene; and dimethylsulfoxide (DMSO).

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, PGMEA, PGME, γ-butyrolactone and EL are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL or cyclohexanone is mixed as the polar solvent,the PGMEA:EL or cyclohexanone weight ratio is preferably from 1:9 to9:1, and more preferably from 2:8 to 8:2. Alternatively, when PGME ismixed as the polar solvent, the PGMEA:PGME weight ratio is preferablyfrom 1:9 to 9:1, more preferably from 2:8 to 8:2, and still morepreferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate In general, the organic solvent is usedin an amount such that the solid content of the resist compositionbecomes within the range from 1 to 20% by weight, and preferably from 2to 15% by weight.

<<Method of Forming a Resist Pattern>>

In the present embodiment, a resist pattern may be formed by forming aresist film on a substrate using the aforementioned resist composition;exposing the resist film; and developing the resist film to form aresist pattern.

The method for forming a resist pattern may be performed, for example,as follows.

Firstly, the aforementioned resist composition is applied to a substrateusing a spinner or the like, and a bake treatment (post applied bake(PAB)) is conducted at a temperature of 80 to 150° C. for 40 to 120seconds, preferably 60 to 90 seconds, to form a resist film.

Following selective exposure of the thus formed resist film, either byexposure through a mask having a predetermined pattern formed thereon(mask pattern) using an exposure apparatus such as an ArF exposureapparatus, an electron beam lithography apparatus or an EUV exposureapparatus, or by patterning via direct irradiation with an electron beamwithout using a mask pattern, baking treatment (post exposure baking(PEB)) is conducted under temperature conditions of 80 to 150° C. for 40to 120 seconds, and preferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment.

The developing treatment is conducted using an alkali developingsolution in the case of an alkali developing process, and a developingsolution containing an organic solvent (organic developing solution) inthe case of a solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. The rinse treatment is preferably conducted using pure waterin the case of an alkali developing process, and a rinse solutioncontaining an organic solvent in the case of a solvent developingprocess.

In the case of a solvent developing process, after the developingtreatment or the rinsing, the developing solution or the rinse liquidremaining on the pattern can be removed by a treatment using asupercritical fluid.

After the developing treatment or the rinse treatment, drying isconducted. If desired, bake treatment (post bake) can be conductedfollowing the developing. In this manner, a resist pattern can beobtained.

In the present embodiment, the developing treatment may be either analkali developing process or a solvent developing process.

(Substrate)

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser, F2 excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. The resist composition of the present invention is effective toKrF excimer laser, ArF excimer laser, EB and EUV.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long as it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

As an example of the alkali developing solution used in an alkalideveloping process, a 0.1 to 10% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) can be given.

As the organic solvent contained in the organic developing solution usedin a solvent developing process, any of the conventional organicsolvents can be used which are capable of dissolving the component (A)(prior to exposure). Specific examples of the organic solvent includepolar solvents such as ketone solvents, ester solvents, alcoholsolvents, amide solvents and ether solvents, and hydrocarbon solvents.Further, the developing solution may contain 80% or more of an organicsolvent.

If desired, the organic developing solution may have a conventionaladditive blended. Examples of the additive include surfactants. Thesurfactant is not particularly limited, and for example, an ionic ornon-ionic fluorine and/or silicon surfactant can be used.

When a surfactant is added, the amount thereof based on the total amountof the organic developing solution is generally 0.001 to 5% by weight,preferably 0.005 to 2% by weight, and more preferably 0.01 to 0.5% byweight.

The developing treatment can be performed by a conventional developingmethod. Examples thereof include a method in which the substrate isimmersed in the developing solution for a predetermined time (a dipmethod), a method in which the developing solution is cast up on thesurface of the substrate by surface tension and maintained for apredetermined period (a puddle method), a method in which the developingsolution is sprayed onto the surface of the substrate (spray method),and a method in which the developing solution is continuously ejectedfrom a developing solution ejecting nozzle while scanning at a constantrate to apply the developing solution to the substrate while rotatingthe substrate at a constant rate (dynamic dispense method).

The rinse treatment using a rinse liquid (washing treatment) can beconducted by a conventional rinse method. Examples of the rinse methodinclude a method in which the rinse liquid is continuously applied tothe substrate while rotating it at a constant rate (rotational coatingmethod), a method in which the substrate is immersed in the rinse liquidfor a predetermined time (dip method), and a method in which the rinseliquid is sprayed onto the surface of the substrate (spray method).

EXAMPLES

The present invention will be described more specifically with referenceto the following examples, although the scope of the present inventionis by no way limited by these examples.

Preparation of Resist Composition: Examples 1 to 14, ComparativeExamples 1 to 6

The components shown in Tables 1 and 2 were mixed together and dissolvedto obtain each resist composition.

TABLE 1 Component (B) Component Component Component Component ComponentComponent (A) (B1) (B2) (B3) (F) (S) Example 1 (A)-1 (B1)-1 (B2)-1(B3)-1 (F)-1 (S)-1 [100] [6.4] [4.0] [3.25] [1.5] [3600] Example 2 (A)-1(B1)-1 (B2)-1 (B3)-1 (F)-1 (S)-1 [100] [6.4] [2.0] [3.25] [1.5] [3600]Example 3 (A)-1 (B1)-1 (B2)-2 (B3)-1 (F)-1 (S)-1 [100] [6.4] [4.2][3.25] [1.5] [3600] Example 4 (A)-2 (B1)-1 (B2)-1 (B3)-1 (F)-1 (S)-1[100] [6.4] [4.0] [3.25] [1.5] [3600] Example 5 (A)-1 (B1)-1 (B2)-1(B3)-1 (F)-1 (S)-1 [100] [6.4] [4.0] [3.25] [1.5] [3600] Example 6 (A)-3(B1)-2 (B2)-1 (B3)-2 (F)-1 (S)-1 [100] [5.8] [3.5] [3.87] [1.5] [3600]Example 7 (A)-4 (B1)-3 (B2)-3 (B3)-3 (F)-1 (S)-1 [100] [6.2] [4.2][3.50] [1.5] [3600] Comparative (A)-1 (B1)-1 — (B3)-1 (F)-1 (S)-1Example 1 [100] [6.4] [3.25] [1.5] [3600] Comparative (A)-1 (B1)-1 —(B3)-1 (F)-1 (S)-1 Example 2 [100] [11.6]  [3.25] [1.5] [3600]Comparative (A)-1 (B1)-1 (B2)-1 — (F)-1 (S)-1 Example 3 [100] [6.4][4.7] [1.5] [3600]

TABLE 2 Component (B) Component Component Component Component ComponentComponent (A) (B1) (B2) (B3) (F) (S) Example 8 (A)-5 (B1)-4 (B2)-1(B3)-2 (F)-1 (S)-1 [100] [8.00] [4.50] [4.10] [1.5] [3600] Example 9(A)-5 (B1)-4 (B2)-1 (B3)-2 (F)-1 (S)-1 [100] [8.00] [2.50] [4.10] [1.5][3600] Example 10 (A)-5 (B1)-4 (B2)-2 (B3)-2 (F)-1 (S)-1 [100] [8.00][6.00] [4.10] [1.5] [3600] Example 11 (A)-5 (B1)-4 (B2)-2 (B3)-2 (F)-1(S)-1 [100] [8.00] [4.50] [4.10] [1.5] [3600] Example 12 (A)-5 (B1)-4(B2)-4 (B3)-2 (F)-1 (S)-1 [100] [8.00] [4.50] [4.10] [1.5] [3600]Example 13 (A)-5 (B1)-4 (B2)-2 (B3)-1 (F)-1 (S)-1 [100] [8.00] [4.50][3.50] [1.5] [3600] Example 14 (A)-6 (B1)-4 (B2)-2 (B3)-1 (F)-1 (S)-1[100] [8.00] [4.50] [3.50] [1.5] [3600] Comparative (A)-5 (B1)-4 (B2)-1— (F)-1 (S)-1 Example 4 [100] [8.00] [2.50] [1.5] [3600] Comparative(A)-5 (B1)-4 — (B3)-2 (F)-1 (S)-1 Example 5 [100] [8.00] [4.10] [1.5][3600] Comparative (A)-5 (B1)-5 (B2)-4 — (F)-1 (S)-1 Example 6 [100][6.00] [1.00] [1.5] [3600] (B2)-5 [5.00]

In Tables 1 and 2, the reference characters indicate the following. Thevalues in brackets [ ] indicate the amount (in terms of parts by weight)of the component added.

(A)-1 to (A)-6: Polymeric compounds (A)-1 to (A)-6 shown in Table 3

(B1)-1 to (B1)-5: Acid generators which are compounds represented bychemical formulae (B1)-1 to (B1)-5 shown below

(B2)-1 to (B2)-5: Acid generators which are compounds represented bychemical formulae (B2)-1 to (B2)-5 shown below

(B3)-1 to (B3)-3: Acid generators which are compounds represented bychemical formulae (B3)-1 to (B3)-3 shown below

(F)-1: fluorine-containing polymeric compound represented by chemicalformula (F)-1 below.

The weight average molecular weight (Mw) and the dispersity (Mw/Mn) interms of the polystyrene equivalent value measured by gel permeationchromatography (GPC) were 15,000 and 1.61, respectively. The compositionof the copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) as determined by ¹³C-NMR was l/m=50/50.

(S)-1: ZX solvent (a mixed solvent of PM (propyleneglycol monomethylether acetate, PGMEA) and PE (propyleneglycol monomethylether, PGME)having a mixing ratio of PM:PE=7:3 (weight ratio))

TABLE 3 Polymeric Copolymer compositional ratio (ratio of compound eachstructural unit (molar ratio)) Mw Mw/Mn A-1 (21)/(22)/(31)/(11)/(13) =2/2/1/3/2 8200 1.56 A-2 (21)/(22)/(31)/(11)/(13) = 2/2/1/3/2 9600 1.60A-3 (23)/(13) = 5/5 6800 1.62 A-4 (21)/(23)/(31)/(13) = 2/2/1/5 89001.55 A-5 (21)/(14)/(31) = 9/7/4 7100 1.68 A-6 (21)/(24)/(14) = 4/2/46000 1.54

In Table 3, the reference characters of each structural unit of thecopolymers indicate the following.

Formation of Solvent Development Negative-Tone Resist Pattern; Examples1 to 7, Comparative Examples 1 to 3

An organic anti-reflection film composition (product name: ARC95,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 90 nm.

Then, the resist composition in Table 1 was applied to the film using aspinner, and was then prebaked (PAB) on a hotplate at a bake temperatureof 110° C. for 60 seconds and dried, thereby forming a resist filmhaving a film thickness of 85 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a phase shift mask (PSM), using anexposure apparatus NSR-S609B (manufactured by Nikon Corporation, NA(numerical aperture)=1.30, Crosspole, immersion medium: water).

Further, a post exposure bake (PEB) was conducted at 90° C. for 60seconds.

Next, a solvent development was conducted at 23° C. for 13 seconds usingbutyl acetate, followed by drying by shaking.

As a result, in each of the examples, a contact hole pattern (hereafter,referred to as “CH pattern”) in which holes having a hole diameter of 43nm are equally spaced (pitch: 90 nm) was formed.

<Evaluation of Negative-Tone Resist Pattern>

[In-Plane Uniformity (CDU) of Pattern Size]

With respect to each CH pattern obtained above, 100 holes in the CHpattern were observed from the upper side thereof using a measuringscanning electron microscope (SEM) (product name: S-9380, manufacturedby Hitachi High-Technologies Corporation; acceleration voltage: 300V),and the hole diameter (nm) of each hole was measured. From the results,the value of 3 times the standard deviation (σ) (3σ) was determined. Theresults are indicated “CDU” in Table 4.

The smaller the thus determined 3σ value is, the higher the level of thedimension uniformity (CD uniformity) of the holes formed in the resistfilm.

TABLE 4 CDU Example 1 3.98 Example 2 4.02 Example 3 3.89 Example 4 3.92Example 5 4.09 Example 6 4.15 Example 7 4.12 Comparative 4.45 Example 1Comparative 4.52 Example 2 Comparative 5.07 Example 3

Formation of Alkali Development Positive-Tone Resist Pattern; Examples 8to 14, Comparative Examples 4 to 6

An organic anti-reflection film composition (product name: ARC95,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 90 nm.

Then, the resist composition in Table 2 was applied to the film using aspinner, and was then prebaked (PAB) on a hotplate at a bake temperatureof 110° C. for 60 seconds and dried, thereby forming a resist filmhaving a film thickness of 90 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a phase shift mask, using an immersionexposure apparatus NSR-5609B (manufactured by Nikon Corporation, NA(numerical aperture)=1.30, Dipole, 0.78/0.97 w/o P).

Subsequently, an alkali developing treatment was conducted for 13seconds using a 2.38% by weight tetramethylammonium hydroxide (TMAH).

Thereafter, a post exposure bake treatment was conducted at 95° C.(PEB(° C.)) for 60 seconds.

As a result, the following line and space pattern (hereafter, referredto as “LS pattern”) was formed.

LS pattern 1: 100 nm pitch/40 nm line, mask size 50 nm

[Evaluation of Line Width Roughness (LWR)]

With respect to each of the LS patterns formed in the manner asdescribed above, the space width at 400 points in the lengthwisedirection of the space were measured using a lengthwise measuringscanning electron microscope (SEM) (acceleration voltage: 300V). As thelengthwise measuring scanning electron microscope, a scanning electronmicroscope manufactured by Hitachi High-Technologies Corporation(product name: S-9380) was used.

From the measurement results of the space widths of each pattern, thevalue of 3 times the standard deviation s (i.e., 3s) was determined, andthe average of the 3s values at 400 points was calculated as a yardstickof LWR. The results are indicated under “LWR” in Table 5.

The smaller the thus determined 3s value is, the lower the level ofroughness of the space portion, indicating that an LS pattern havingspaces with a uniform width was obtained.

TABLE 5 LWR Example 8 2.70 Example 9 2.76 Example 10 2.65 Example 112.65 Example 12 2.81 Example 13 2.64 Example 14 2.65 Comparative 3.02Example 4 Comparative 3.15 Example 5 Comparative 3.67 Example 6

As seen from the results shown above, the resist patterns formed usingthe resist composition of the present invention containing all of theacid generator (B1), the acid generator (B2) and the acid generator (B3)exhibited excellent CDU and LWR.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resist composition comprising: a base component(A) which exhibits changed solubility in a developing solution underaction of acid, and an acid-generator component (B) which generates acidupon exposure, the acid-generator component (B) comprising at least oneacid generator (B1) represented by general formula (b1-1), (b1-2) or(b1-3) shown below, at least one acid generator (B2) represented byformula (B2)-1 or (B2)-2 shown below, and at least one acid generator(B3) represented by general formula (b3) shown below:

wherein R″¹⁰¹ represents an aliphatic cyclic group which may have asubstituent, a group represented by any one of formulae (r-hr-1) to(r-hr-6) shown below or a chain-like alkyl group which may have asubstituent; R″¹⁰² represents an aliphatic cyclic group which may have asubstituent, a lactone-containing cyclic group represented by any one ofgeneral formulae (a2-r-1) to (a2-r-7) shown below or an —SO₂— containingcyclic group represented by any one of general formulae (a5-r-1) to(a5-r-4) shown below; R″¹⁰³ represents an aromatic cyclic group whichmay have a substituent, an aliphatic cyclic group which may have asubstituent or a chain-like alkenyl group which may have a substituent;V″¹⁰¹ represents a fluorinated alkylene group; L″101 represents —C(═O)—or —SO₂—; v″ represents an integer of 0 to 3; q″ represents an integerof 1 to 20; n″ represents 0 or 1; and each M₁ ⁺ independently representsa monovalent organic cation:

wherein each Ra′²¹ independently represents a hydrogen atom, an alkylgroup, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group;R″ represents a hydrogen atom or an alkyl group; A″ represents an oxygenatom, a sulfur atom or an alkylene group of 1 to 5 carbon atoms whichmay contain an oxygen atom or a sulfur atom; n′ represents an integer of0 to 2; and m′ represents 0 or 1;

wherein each Ra′⁵¹ independently represents a hydrogen atom, an alkylgroup, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group;R″ represents a hydrogen atom or an alkyl group; A″ represents an oxygenatom, a sulfur atom or an alkylene group of 1 to 5 carbon atoms whichmay contain an oxygen atom or a sulfur atom; and n′ represents aninteger of 0 to 2

R²—COO⁻M₂ ⁺  (b3) wherein R³ represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent, or achain alkenyl group which may have a substituent; and M₃ ⁺ independentlyrepresents a monovalent organic cation.
 2. The resist compositionaccording to claim 1, further comprising a photoreactive quenchercomponent (D).
 3. The resist composition according to claim 1, whereinthe base component (A) is a base component which exhibits increasedsolubility in a developing solution by the action of acid.
 4. The resistcomposition according to claim 1, further comprising a fluorine additivecomponent (F) having a molecular weight of 1,000 or more.
 5. A method offorming a resist pattern, comprising: using a resist compositionaccording to claim 1 to form a resist film on a substrate, exposing theresist film, and alkali developing the resist film to form a resistpattern.
 6. A method of forming a resist pattern, comprising: using aresist composition according to claim 1 to form a resist film on asubstrate, exposing the resist film, and developing the resist filmusing a developing solution containing 80% or more of an organic solventto form a resist pattern.
 7. The resist composition according to claim1, wherein, in general formula (b3), R³ represents an aromatichydrocarbon group which may have a substituent, an aliphatic cyclicgroup which may have a substituent and a chain hydrocarbon group whichmay have a substituent, the aromatic hydrocarbon group is a phenyl groupor a naphthyl group, the aliphatic cyclic group is a group in which oneor more hydrogen atoms have been removed from adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane, and the chainhydrocarbon group is a chain alkyl group having 1 to 10 carbon atoms.